

316 WHAT IS A DESMID? 
at one time supposed to belong to this family, have been 
since proved not to be members of it. It has been said that 
hardly a specimen of fresh water can be found that does not 
serve as the habitation of Desmids, but such is not strictly 
the case, although it is true that they are very widely dis- 
tributed, and one intending to study them should have no 
difficulty in procuring specimens for examination. In clear 
pools, in open exposed situations, they occur in the greatest 
abundance, the largest species being generally found nearest . 
the bottom. Sometimes they are to be found adhering in 
large quantities to some of the submerged aquatic plants 
that grow in such localities, forming investing films of a 
bright green color, which can be removed from its support, 
or is best gathered along with it. At other times they rest 
as a thick coating upon the bottom, or float in the form of a 
bright green scum upon the surface; but the last mode of 
occurrence is by no means common, the green-colored film 
seen so frequent upon pools not being Desmids but mem- 
bers of a group into which have been placed the Protococ- 
cus, Euglenia, and the so-called “Red-snow.” Of these we 
may have something farther to say hereafter, as they are 
possessed of wondrous characteristics, and present subjects 
well worthy the study of any one having a microscope. The 
brownish seum which is so commonly seen in marshes and 
ponds does not consist of Desmids either, but is mostly made 
up of myriads of plants very nearly related to them, an 
familiarly known as Diatoms. These, again, are of extreme. 
beauty, and at the present day hundreds of microscopes are 
turned towards them endeavoring to fathom their mysteries, 
and the optician’s skill has been brought to bear upon the 
construction of lenses specially for the purpose of studying 
their life, history, and structure. 
a T smids, Desmidiew, or, more correctly speaking; 
— Desmidiacee, have had this designation applied to them 
from their form, that is to say, on account of their being - 
made up of two symmetrical halves, united together by 




